Protecting covering for rubber sheets



Patented Apr..2 6, I927.

'UNHTED STATS PTENT" OFFICE.

GUSTAVUS J. ESSELEN, JR., F SWAMPSCOTT, MASSACHUSETTS.

PROTECTING COVERING FOR RUBBER SHEETS.

Application filed March 29, 1924. Serial No. 702,771.

' keep the sheets from sticking together. The

' usual material used for this purpose is the so called holland madefrom a strong cotton fabric which is provided with a smooth glaze. Thisfabric is smooth enough sothat it .can be stripped from the stickysurface of unvulcanized rubber and is strong enough so as not to readilytear when stripped off. The material, however, is expensive. Ihavediscovered that the paper known to the trade as glassine paper may beemployed as a satisfactory and inexpensive substitute for the fabricholland as a protecting coating for sheet rubber. This glassine paper isa stock product and can be easily obtained and may be used withoutspecial treatment. This paper is mechanically tough, it has a highlyglazed Surface which permits it to be readily stripped from the surfaceof unvulcanized rubber, and has a homogeneous substantially transparentbody through which the surface of the rubber is visible for inspection.Glassine paper ismade from cellulose pulp which has been mechanicallyhydrated. It is made by a wet milling process in which the cellulosefibers are subjected to crushing andrubbing in the presence of water.This mechanical action is carried to a point where the cellulose fibersare reduced to a hydrated pulp, from which the glassine paper is made.The sheet' "formed from the hydrated cellulose pulp is passed in a moistcondition between highly polished heater calender rolls under pressurein order to give it a smooth highly glazed surface. The term glassinepaper is ordinarily employed in the trade to describe a paper havin aglass-like or glazed surface and made rom mechanically hy-- dratedcellulose pulp, as distinguished from chemically parchmentized papers.Paper is ordinarily chemically parchmentized by passing a sheet of theformed paper through a bath of sulphuric acid which superficiallydissolves the surfaces of the sheet, leaving the fibers in the interiorof the sheet subas a kraft paper.

stanti ally unaffected. This chemically parchmentized paper does nothave the homogeneous substantially transparent body of glassinepaper.The chemical parchmentizing treatment does not produce a glazed surfacelike that of glassine paper, but on the contrary produces acharacteristic uneven cockled surface which it is very difficult, if notimpossible, to eliminate by calendering. Moreover, the chemicalparchmentizing treatment leaves certain chemical residues in the paper,which, unless the greatest pains are taken to remove them, WOUlCl have adeleterious effect, in time, on

the paper-or on rubber in contact with the paper or on both. Suggestionshave been made to employ chemically parchmentized paper as a liner forsheet rubber, but if so used it would require special calendering andsoftening treatment before it could be used at all, whereas glassinepaper may be employed without such speclal treatment.

In Figures 1 and-2 of the drawings is illustrated the rubber sheet withthe glassine paper protective coating applied thereto. In these drawings1 indicates the rubber sheet and 2 the glassine paper protectivecoating.

While the glassine paper, if made'with a moderately heavy body, hassuflicient strength to enable it to be stripped from the rubber, it maybe combined with a backing of a stronger or heavier bodied paper, suchemployed in the paper trade to designate certain papers of specialquality having unusually tough fiber, the word being adopted from theGerman word kraft whlch means strength. A compositeprot'ecting"sheet forrubber may be made from a 'backing of a heavier paper, such as a kraftpaper, and a facing of glassine paper on one or both sides of thebacking,and secured thereto by a flex ible adhesive such, for example,as a flexible glue made from animal glue glycerine'and water. I

In Figure 8 is illustrated diagrammatically the modification of theinvention, and in which 1 indicates the rubber sheet, 2 the glassinepaper and 3 the" backing of kraft paper. 7

While the preferred embodiment of the The term kraft paper is' presentinvention has been specifically de- I scribed it is to be understoodthat the invention is not limited to all of the details hereembodiedwithin e e 05 of the following claims. ,4

I claim: I

1. The combination with a sheet of rubber, of a readily separableprotecting sheet of smooth surfaced glassine paper, substantially asdescribed.

2. The combination with a sheet of rubber, of a readily separableprotecting sheet of paper made from mechanically hydrated cellulose pulpand having a smooth highly glazed surface which permits it to be readilystripped from the rubber, substantially as described.

3. The combination with a sheet of rubber,

of a readily separable protecting sheet of paper having a substantiallytransparent homogeneous body made from mechanically hydrated cellulosepulp and having a smooth highly glazed surface which permits itto bereadily stripped from the rubber, substantially as described.

4. The combinationwith a sheet of rubber, of, a readily separableprotecting sheet of paper formed from a hydrated cellulose pulp into asubstantially transparent homogeneous sheetand calendered to give it asmooth highly glazed surfacewhich permits it to be readily stripped fromthe'rubber, said paper being employed Without chemical parchmentizingtreatmentvor impregnation with softening agents, substantially asdescribed.

5. The combination with a sheet of rubber,

cellulose pulp and having a highly glazed surface which permits it to bereadily stripped from the rubber, and having a strengthening backing ofa heavier tough fiberedpaper, substantially as described.

7. The combination with a sheet ofrubber,

of a readily separable protecting sheet of paper made from' mechanicallyhydrated cellulose pulpand having a highly glazed surface which permitsit to be readily stripped from the rubber, and having -a strengtheningbacking of a tough fibered stronger paper secured thereto with aflexible adhesive, substantially as described.

8. The combination with a sheet of rubber,

of areadily separable protecting composite. sheet of paper formed of astrengthening paper backing, and a facing on both sides thereof composedof a highly glazed paper made from mechanically hydrated cellulose pulp,substantially as described.

In testimony whereof I have hereuto set my hand.

GUSTAVUS J ESSELEN, J R.

